page_title: Juan de la Cierva
section_title: The gyroplane (autogyro)
hierarchical_section_title: Juan de la Cierva / The gyroplane (autogyro)
caption_attribution_description: English: Pitcairn PCA-2 autogiro (NACA44), flown at Langley for the NACA investigation of an rotor systems.
context_page_description: Juan de la Cierva y Codorníu, 1st Count of la Cierva was a Spanish civil engineer, pilot and aeronautical engineer. His most famous accomplishment was the invention in 1920 of the first helicopter called Autogiro, a single-rotor type of aircraft that came to be called autogyro in the English language. In 1923, after four years of experimentation, De la Cierva developed the articulated rotor, which resulted in the world's first successful flight of a stable rotary-wing aircraft, with his C.4 prototype.
  De la Cierva was born to a wealthy family. After several successful experiments with aviation as a boy, he eventually earned a civil engineering degree. He moved to the United Kingdom in 1925 where, with the support of Scottish industrialist James G. Weir, he established the Cierva Autogiro Company.
  At the outbreak of the Spanish Civil War, De la Cierva supported the National forces, helping the rebels to obtain the De Havilland DH-89 'Dragon Rapide' which flew General Franco from the Canary Islands to Spanish Morocco. His brother was killed by the Republican army in Paracuellos del Jarama.
context_section_description: De la Cierva started building the aircraft in 1912, and in 1919 he started to consider the use of a rotor to generate lift at low airspeed, and eliminate the risk of stall.
  In order to achieve this, he used the ability of a lifting rotor to autorotate, whereby at a suitable pitch setting, a rotor will continue to rotate without mechanical drive, sustained by the torque equilibrium of the lift and drag forces acting on the blades. This phenomenon was already known, and was available as a safety feature to allow controlled descent of a helicopter in the event of engine failure. With De la Cierva's autogyro, the rotor was drawn through the air by means of a conventional propeller, with the result that the rotor generated sufficient lift to sustain level flight, climb and descent.
  Before this could be satisfactorily achieved, De la Cierva experienced several failures primarily associated with the unbalanced rolling movement generated when attempting take-off, due to dissymmetry of lift between the advancing and retreating blades. This major difficulty was resolved by the introduction of the flapping hinge. In 1923, De la Cierva's first successful autogyro was flown in Spain by Lt. Gomez Spencer.
  This pioneering work was carried out in De la Cierva's native Spain. In 1925 he brought his C.6 to Britain and demonstrated it to the Air Ministry at Farnborough, Hampshire. This machine had a four blade rotor with flapping hinges but relied upon conventional airplane controls for pitch, roll and yaw. It was based upon an Avro 504K fuselage, initial rotation of the rotor was achieved by the rapid uncoiling of a rope passed around stops on the undersides of the blades.
  The Farnborough demonstration was a great success, and resulted in an invitation to continue the work in the UK. As a direct result, and with the assistance of the Scottish industrialist James George Weir, the Cierva Autogiro Company, Ltd., was formed the following year. From the outset De la Cierva concentrated upon the design and the manufacture of rotor systems, relying on other established aircraft manufacturers to produce the airframes, predominantly the A.V. Roe Company.
  The Avro built C.8 was a refinement of the C.6, with the more powerful 180hp Lynx radial engine, and several C.8s were built. The C.8R incorporated drag hinges, due to blade flapping motion causing high blade root stresses in the rotor plane of rotation; this modification resulted in other problems such as ground resonance for which drag hinge dampers were fitted.
  The resolution of these fundamental rotor problems opened the way to progress, confidence built up rapidly, and after several cross-country flights a C.8L4 was entered for the 1928 Kings Cup Air Race. Although forced to withdraw, the C.8L4 subsequently completed a 4,800 km (3,000 mi) tour of the British Isles. Later that year it flew from London to Paris thus becoming the first rotating wing aircraft to cross the English Channel. The tour was subsequently extended to include Berlin, Brussels and Amsterdam.
  A predominant problem with the autogyro was driving the rotor prior to takeoff. Several methods were attempted in addition to the coiled rope system, which could take the rotor speed to 50% of that required, at which point movement along the ground to reach flying speed was necessary, while tilting the rotor to establish autorotation.
  Another approach was to tilt the tail stabiliser to deflect engine slipstream up through the rotor. The most acceptable solution was finally achieved with the C.19 Mk.4, which was produced in some quantities; a direct drive from the engine to the rotor was fitted, through which the rotor could be accelerated up to speed. The system was then declutched prior to executing the take-off run.
  As De la Cierva's autogyros achieved success and acceptance, others began to follow and with them came further innovation. Most important was the development of direct rotor control through cyclic pitch variation, achieved initially by tilting the rotor hub and subsequently by Raoul Hafner by the application of a spider m
caption: Pitcairn PCA-2 autogyro, built in the US under Cierva license, 1961.
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